dtfile: Enable FILE_MAP_OPTIMIZE on FreeBSD. This avoids unnecessary tt_file_netfile calls on local host.

cde/programs/dtfile/Imakefile

@@ -39,6 +39,7 @@ EXTRA_INCLUDES = -I/usr/include/freetype2
 
 #if defined(BSDArchitecture)
 EXTRA_INCLUDES = -I$(XPROJECTROOT)/include/freetype2
+EXTRA_DEFINES = -DFILE_MAP_OPTIMIZE
 #endif
 
 SRCS =  ChangeDir.c     ChangeDirP.c    Command.c       Common.c \